I have just been thinking about the exact same problem. Two sound source with only one speaker, amp system.
My headunit uses stereo and my PC give out 5.1dolby digital. I could either just have stereo output from my PC to my headunit and then goes to the speaker, but I think it's such a waste to not use the 5.1 when it's avaliable.
I am really interested in a device that would allow me to switch between source.
Actaully I have a question, my headunit is a Pioneer with indash screen. It has Dolby Pro Logic. When I have it on, it will seperate my stereo audio source into front left, center, front right, rear left, rear left, and sub. How does it compare with real 5.1 dolby digital ?
If I am playing a DVD movie with 5.1 out from the computer but only uses stereo output , when it goes into my headunit with the Dolby Pro Logic on, will I be losing a lot of special effects ?